This invention relates to Rapid Solidification Processing (R.S.P.) techniques and more particularly to melt spin chill casting wherein quench rates and heat flux dissipation higher than the prior art are achieved.
Melt spin chill casting is a method wherein a jet of hot molten material, generally metal, impinges upon a chilled moving quench (chill) surface and the molten material is rapidly quenched, at rates of 10.sup.3 to 10.sup.7 .degree.C./sec. This technique has been employed to produce polycrystalline products possessing very fine crystalline structure and more recently to produce glassy or amorphous metal filaments having superior commercially interesting physical properties.
A critical factor in both the ability to prove the needed high quench rates and to obtain economical production rates is the ability of the rotating quenching wheel to efficiently and rapidly remove the heat yielded by the rapidly chilled material. Complete quenching should be effected before centrifugal forces cause the solidified material to leave the wheel. Reference in this regard is made to U.S. Pat. No. 3,862,658 issued Jan. 28, 1975 to Bedell.
Efficient and effective melt spin chill casting depends upon two parameters. One is that the heat be removed from the rotating quench wheel as rapidly as it is transferred from the molten material an the second is that the temperature of the chill surface be maintained as low as possible to obtain the highest possible quench rate. To meet these requirements, hollow liquid cooled casting wheels have been developed.
Examples of such devices are described in U.S. Pat. Nos. 4,307,771 issued Dec. 29, 1981 to Draizen et al.; 4,489,773 issued Dec. 25,1984 to Miller; 3,881,540 issued May 6, 1975 to Kavesh; 4,281,706 issued Aug. 4, 1981 to Liebermann et al; 3,938,583 issued Feb. 17, 1976 to Kavesh; 3,845,810 issued to Gerding on Nov. 5, 1974, 4,502,528 issued to Frissora et. al. on Mar. 5, 1985; and 4,537,239 issued to Budzyn et. al. on Aug. 27, 1985. Other examples of such devices are found in Japanese Pat. Nos. 57-187147 (Nov. 17, 1982); 57-190753 (Nov. 24, 1982); 57-190754 (Nov. 24, 1982); and 59-42160 (Mar. 8, 1984).
Other examples of casting wheels are provided in U.S. Pat. Nos. 2,825,108 issued Mar. 4, 1958 to Pond, and 2,899,728 issued to Gibbons, and 4,142,571 issued Mar. 6, 1979 to Narasimhan.
The prior art liquid cooled casting wheels, however, provide relatively low rates of heat removal from the chill surface; the devices tend to be subject to deficiencies on the flow of liquid coolant, such as, for example, cavitation, and generation of stable flow patterns. Thus, in order to provide adequate lateral diffusion of heat to spread the heat load and prevent burn out, relatively thick chill walls (i.e. a large distance between the chill surface on which the molten metal impinges and the heat exchange surface are often necessitated.
Further, such devices tend to require high velocity differentials between the chill wheel surface and molten metal jet to provide adequate heat transfer. This high velocity tends to cause geometric distortion of the molten metal when it strikes the chill wheel surface, making production of wide continuous sheets of material difficult; current devices are capable of effectively producing ribbons of only a few centimeters in width.